The treatment of choice for fractures of the shaft of the femur is the intramedullary (IM) nail, a long tubular rod that spans the fracture and often needs to be fastened to the bone at both ends with transverse screws placed through openings at both the proximal and distal ends of the nail. The screws at the proximal end are close to the surgical incision and are fairly easy to insert, but the openings at the distal end, hidden as they are, deep within the bone and soft tissues, present a challenge to locate and to place screws through them. As a result, there have been numerous inventions attempting to solve this problem, the commonest being an external side arm drill jig, in which a long arm placed external to the patient's limb and parallel to the nail, is fastened to the proximal end of the nail, while the distal end of the arm comprises a drill jig, which is expected to line up with the nail openings. Unfortunately, the nail often bends and twists during its insertion and as a result, the openings are not where they were expected to be, rendering the jig useless. Other similar inventions have used adjustable side arms to compensate for this bending and twisting, with or without the use of x-rays to help align the arms and their drill jigs with the nail openings. Typical of these is US 2008/0281331 A1.
Other inventions used small magnets placed within the distal end of the nail, and which are sensed with other magnets to help locate the openings in the IM nail such as U.S. Pat. No. 7,753,913.
Still other inventions used electromagnetic coils placed within the distal end of the nail, which are sensed and their signal displayed on a monitor to show the location of the openings and direct a drill guide such as U.S. Pat. No. 7,060,075.
Others use x-rays to locate the openings in conjunction with co-axial laser beams to assist in the placement of a drill to bore openings in the bone in line with the openings in the nail, such as U.S. Pat. No. 5,426,687. Many of these systems use a remote monitor to display the rod openings, and require the surgeon to manipulate a drill freehand while watching the display, relying on the surgeon's skill to find the openings in the IM rod, such as U.S. Pat. No. 4,803,976.
Others use a C-arm fluoroscope and computers to calculate the location of the openings in the IM nail and then instruct a robot to drill the openings in the bone based on this information, an approach too expensive for many hospitals. Examples are US 2008/0281334 A1, and US 2009/0043190A1.
Currently, many surgeons prefer to use the tried and true method of using the C-Arm fluoroscope to locate the openings and then use a drill freehandedly to drill the openings in the bone and insert the screws. In this method, a C-arm fluoroscope is rotated around the limb, providing instant images which can be viewed on a monitor. In use, the C-arm shows the distal end of the nail and its screw openings. The C-arm is then manipulated until the openings on both sides of the nail become superimposed on each other, creating an undistorted “perfect circle”, which proves that the x-ray beam is properly aligned with the openings. In a slight variation of this technique, thought to be a little faster, radio-opaque wires are taped to the image intensifier receiver, perpendicular to each other and centered on the receiver. The C-arm is then manipulated until the nail openings are centered on each other and over the crossed wires, which is proof that the central x-ray beam is aligned with the openings. A pencil mark or an incision, or both, is made on the skin over the displayed opening and through it, a drill is hopefully aligned freehand with the x-ray beam and an opening made through the bone, and, depending on skill and luck, through the opening in the nail and the opposite bone cortex. Often, however, multiple attempts are required, and it has been estimated that this phase of the operation takes more time than the rest of the operation, with more x-ray exposure to the surgeon, the staff and the patient, as well as the added expense.
The present invention is a targeting device in which the targeted location is not the actual location of the openings in the distal end of the IM nail as in the prior art, but is instead, the location of the x-ray beam on the outer surface of the thigh as it traverses the surface and through the “perfect circles” that the nail openings create when exhibited on the fluoroscope's monitor.